This invention relates to a television camera device, which comprises a camera head and a camera control unit for converting video signals obtained from the camera head into corresponding television signals and also for supplying camera head control signals to the camera head.
The television camera device which is used in the studios of television broadcasting stations usually comprises a camera head including an image pick-up tube and a camera control unit for producing a television signal by combining a video signal obtained from the camera head and sync. signals and also for supplying control signals for controlling the optical system, for instance diaphragm and zooming control signals, to the camera head. The camera head is connected to the camera control unit through a camera cable. The camera cable that is used transmits a number of different signals independently of one another, and is usually a multi-core cable, which is heavy and sometimes troublesome when moving the camera head.
In order to eliminate such inconvenience, it has been thought to transmit signals in the form of a multiplexed signal so as to permit use of a thinner and lighter cable. In this case, while the transmission of signals in the multiplexed form between the camera control unit and camera head is possible, there is a problem in the power supply from the former to the latter. Power may be supplied either through an AC or a DC system. In the case of the AC system, it may be thought to supply AC power from the camera control unit to the camera head without using any exclusive transmission line to this end but by making use of, for instance, shield conductors employed in the camera cable. This attempt, however, is prone to electric shock accidents since the shield conductors are usually grounded. To prevent this, it is necessary to provide an insulation transformer or the like within the camera head, and such an insulation transformer increases the bulk and weight of the camera head.
In the case of the DC system, it is necessary to provide a DC-to-AC converter in the camera head since the diaphragm mechanism, zooming mechanism, etc. in the optical system of the camera head require AC power for driving them. The provision of the DC-to-AC converter in the camera head which has a limited space is again undesired from the standpoint of reducing the size and weight of the camera head.